Defines how tooltips are positions.

<div class="definition">
    String, default = 'top'
</div>

The <span class="argument">.tooltip</span> can be either 'top', 'bottom', 'left', 'right' and define how tooltip will be displayed. You will still need to set
<span class="property">.tooltip</span> of each tab for which you need tooltip.
<div style="height: 10px"></div>

You can defined it during object creation:
<textarea class="javascript">
let tabs = new w2tabs({
    name: 'tabs',
    tooltip: 'bottom',
    tabs: [
        { id: 'tab1', text: 'Tab 1', tooltip: 'Tab 1 tooltip' },
        { id: 'tab2', text: 'Tab 2', tooltip: 'Tab 2 tooltip' }
    ]
});
</textarea>

Or any time during run-time:
<textarea class="javascript">
w2ui.tabs.tooltip = 'top';
</textarea>

No refresh is needed